Compass system



A, A. STUART, JR

MBrch Q, 1943.

COMPASS SYSTEM Filed NOV. 5, 1940 2 Sheets-Sheet 1 REMUTE INDICATOR TD EITHER REMOTE.

' INDICATORS MASTER INDICATOR) roam-111w:

' IATTOYRN'EY.

943. A. A. STUART, JR 2,313,682

COMPASS SYSTEM Filed Nov. 5, 1940 2 Sheets-Sheecl 2 A lfre i Shani-I1 EMMA/w:

ATTORNEY.

Patented Mar. 9, 1943 UNITED STATES PATENT OFFICE COMPASS SYSTEM Alfred A. Stuart, Jr., Hasbrouck Heights, N. J., as-

signor to Bendix Aviation Corporation, South Bend, Ind, a corporation of Delaware Application November 5, 1940, Serial No. 364,444

This. invention relates to navigational compasses and particularly to a compass system in 7 motor which will minimize the effects of hunt ing.

A further object of the invention lies in the provision of a novel means for transferring electrical energy from a rotating shaft to a fixed point.

Other objects include the provision of aco pass system in which a course may be easily set out and interpreted and in which low directive electrical forces may be amplified in order to give accurate bearing indications at a number of sta- ,tions.

These and other objects of the present invention will become readily understood upon a study of the following specification when made in con- Junction with the attached drawings, throughout which like parts are designated by like reference characters.

Fig. 1 is a representation, partly schematic, and partly in perspective, of a compass system of the present invention.

Fig. 2 is a longitudinal sectional view of a motor which is part of the present invention; and

Fig. 3 is a sectional view of a novel type of electrical coupling which is employed in the present invention.

Generally speaking, the present invention comprises a compass system which may be of the magnetic needle type, or the earth inductor type,

. connected in series with coil 20.

magnetic fiux gate of permeable material, such as Mumetal or "Permalloy, having an exciting winding ii carried by an inner portion of each of legs l2, and connected to alternator it through leads l4. Legs i2 also carry output windings ii which are connected through leads 1 ii to the stator portion ll of the motor 01' a selfsynchronous system, such as an Autosyn it,

which has a rotor portion l8, carrying a coil 2ii.

Stator portion I! is of the well-known type having three symmetricallyspaced taps (e. g., as shown in Reichel et a1. Patent No. 2,038,059) to which are connected the leads I. Rotor I8 is connected to a shaft 2i, which carries a core member 22 of magnetic material, such as soft iron, about which is wound primary winding 23 Surrounding core 22 and coil is a shell member 24 of magnetic material, such as soft iron, and internally of which there is wound a secondary winding 25,

having output leads 2i and 21 connected to the input of a vacuum tube amplifier 28, of any wellknown design, which is energized by alternator I I through leads l3. Core member 22 is separated from shell member 24 by an air gap 29, which is suillcient to prevent frictional engagement of elements 22 and 24, but which'preferably has as low a width as is possible in shop practices.

, The output of amplifier 28 is connected through leads 38 to one phase winding ii of twophase induction motor 12. Phase winding ii and another phase winding 33 are wound within a stator member 34 of iron laminations in the manner usual for atwo-phase stator winding. Phase a winding 83 is energized by alternating current utilizing a flux gate and a torque amplifier, similar in some respects to the type described in apfor transferring electrical energy from a rotating shaft to a fixed position, and also, a new type of induction motor, the rotor of which has a moment of inertia of a value appreciably less than that of the conventional induction motor.

Having reference to Fig. 1, i0 designates afrom alternator 35 through leads 38. A second stator portion 31 of iron laminations is fixed within stator 24 and separated therefrom by an air gap 38, The cylindrical wall 39 of acupshaped member 40 is contained within air gap 38, and is mounted to rotate therein upon rotation of shaft 4i to which it is afiixed in a manner shown more specifically in Fig. 2. Shaft 4i is connected to shaft 2| through any suitable reduction gears 42, and rotation of shaft 2i will move pointer 48, which is fixed to the outer end of a stub shaft 44. Motion is transmitted to shaft 44 from shaft 2| by means of gears 45 and 48 which are in engagement with intermeshed pinions 41 and 48, respectively.

For a purpose to be described below, means are provided for the simultaneous rotation of pointer 43 and scale 49. For this reason, a knob 50 is connected to a pinion II through a shaft 52, pinion 5| drives a gear 53, which meshes with a spur gear 54, which is fastened to the under-side of scale 49 by means oi screws 55. With this arrangement, rotation of knob 50 will of course, cause scale 49 to rotate through the action of the gear train, just described. Lubber lines 56 are fixed with respect to a selected axis of a carrying vehicle, such as an aircraft or marine vessel, and are provided so that an operator in turning knob 50, may indicate a course upon which the vehicle is to be headed. When, upon rotation of scale 49, the value of the selected course appears equally between each of the lubber lines 56, the vehicle may be then steered until pointer 43 falls between the lubber lines 56, and in this condition pointer 43 and scale 49 indicate that the vehicle is headed on the selected course.

Rotation of scale 49 through a definite are (by manipulation of knob 50), without 9. corresponding rotation of pointer 43 through the same are, would cause an error to be introduced between the scale 43 and the pointer 43. In order to obviate the introduction of an error of this type, a planetary gear arrangement, of which gear 45 becomes the central or sun gear, and pinions 41 and 48 become planet gears, is provided. Gear 45 is intended to be rotated only through the action of motor 32 since shaft 2| is rotatable only by operation of motor 32. Gear 53 is attached to a pinion 51 by means of a shaft 58, which pinion engages with planetary gear 59. Gear 59 carries spindles 60 and 6| of pinions 41 and 48 respectively, which pinions are freely rotatable about these spindles. When the pilot or navigator turns knob 50 to rotate scale 49, pinion 51 will be rotated by motion of gear 53 causinggear 59 to rotate the spindles 58 and 6| through an are about shaft 2| as a center. In rotating about gear 45, which remains fixed if motor 32 is still, pinions 41 and 48 are made to turn and transmit angular motion to gear 46 which of course, rotates pointer 43. Since it is desired to rotate scale 49 and pointer 43 through equal angles upon manipulation of knob 50, the gear system above described for rotating pointer 43, can be readily designed to have the same value as the gear train which causes rotation of scale 48.

Lubber lines 56 may be horizontal and parallel to the fore and aft axis of the carrying vehicle, or they may be vertically disposed, that is, at right angles to the fore and aft axis of the vehicle but parallel to the vertical plane passing through the fore and aft axis of the vehicle. In order to set a desired course, without disturbing the operation ofgnotor 32, it is necessary only for a navigator toturn knob 5|! until the numerical value of the course shown on scale 49 -appears within lubber lines 56. It will be readily understood, of course, that the manual course selection may be obtained through rotation of knob 50, regardless of whether gear 45 is at rest or is being rotated by motor 32. Any variation from the course selected will readily appear as a left or right deviation of pointer 43, and maintenance of the desired course may be obtained by merely steering the vehicle so as to keep pointer 43 from varying to the right or left of the selected course.

The operation of a compass system having a flux gate, such as "I, connected to an Autosyn, such as l8, in a manner so that the voltage induced in the rotor of the Autosyn may be amplified, and used to energize one phase, of a twophase induction motor, is fully described in the above-identified application Serial No. 340,396

but a brief description of the system shown in Fig. 1 will now be given so that its operation will be readily understood.

When alternating current from alternator |3 energizes winding II, at a certain value of cur rent between zero and maximum in each half cycle, which value may be readily determined by experiment, the portion of legs l2, immediately adjacent and surrounding the three portions of windings II, will become saturated and will remain saturated until the value of the alternating current in each half cycle falls below the level necessary to maintain saturation. For each interval, in which the alternating current maintains the inner portion of legs l2 saturated, the earths field is prevented from threading in sequence through legs l2, and is forced to travel completely or partially through air in threading from one of legs 2| to the others. This change in the path of the earths fiux causes a change in the number or lines of fiux threading the three legs l2, and voltages are induced in the output windings l5 due to this change of flux. These voltages are carried. through leads |6 to a stator ll of Autosyn receiver I8, and induce a resultant voltage in the winding 2|! of rotor I9. Upon induction of a voltage therein current flows in coil 20 and in winding 23 which is in series with coil 20. This voltage is alternating at the frequency of the alternating current set up in output windings |5, and is transferred by electromagnetic induction to the secondary winding 25. The magnetic core 22 and the magnetic shell 24, which enclose windings 23 and 25, increase the magnetic fiux in the local magnetic circuit between windings 23 and 25, increasing the inductance, and therefore increasing the voltage induced in secondary winding 25 by the current in primary winding 23 over that which would be induced in the absence or the magnetic circuit shown. The alternating current voltage induced in secondary 25 is led to the'input of vacuum tube amplifier 28 through leads 26 and 21, and is amplified to any desired value, and after amplification is led through conductors 30 to the phase winding 3| of two-phase motor 32. Since the other phase winding 33 is constantly energized by alternator 35 through leads 36, upon voltage being impressed upon phase winding 3|, motor 32 rotates shaft 2| and pointer 43, until voltage is removed from phase winding 3|.

Voltage will be removed from phase winding 3| when rotor |9, which is carried by shaft 2|, has been turned to the null point of the voltages induced in stator portion I! by means of output windings l5. The voltages induced in stator portion i! have a single-phase relation to each other and vectorially, they can be combined into a single resultant voltage which, upon induction into rotor and after amplification in amplifier 28, will energiz phase winding 3 causing induction motor 32 to rotate rotor I! to a null position; that is, the position in which the plane of the rotor coil is parallel to the resultant field of stator portion H. A; the resultant field depends on the angular disposition of the legs of flux gate H) in the horizontal plane of the earths field and since this null position will be rotated degree for degree upon rotation of the fiux gate, it will be seen that indications of azimuth may be had through 360 degrees.

There are two null positions degrees apart, but ambiguity is avoided, since upon one null position being assumed by the rotor I3, it can not thereafter align itself with the null position 180 degrees away, as the phase reversal incident upon the rotors passing through the null will cause the magnetic held of the current in rotor I9 to react with the field of the resultant current in stator I'I so as to always turn rotor IS in the direction corresponding to the direction of rotation of flux gate III.

Reference to Fig. 1 indicates that alternators I3 and 35 are connected by a common shaft to the rotor of a D. C. motor I6, which is preferably of any conventional constant speed design, and which is energized by means of a storage battery, not shown. Alternator I3 energizes the saturating winding H (through conductors I4) at any desired frequency, for example 400 cycles.

age in coils I5 at each of these points. These pulseswill be alternately of opposite sign, since at $5 and 225 degrees the earths flux is leaving legs I2 and at 135 and 315 degrees, it is entering legs I2, thus cutting coils I5 in opposite directions, and when resonated, these pulses are smoothed out into sine waves and since there are Current from alternator 85 is of double the frequency of current from alternator I3 (800 cycles) and is connected through leads 36 to one phase winding 33. Since the other phase winding 3| is energized, as above stated, by energy from the output of coils I5 as amplified in the vacuum tube amplifier 28, it will be appreciated that inordelf to obtain operation or twfi-phase induction mo tor 31, the frequency of phase 3I must be equal to the frequency of phase 33. It is necessary to double the frequency of phase winding 33, in order that its frequency might be equalto the frequency in phase winding 3|, because in the operation of saturating a portion of legs I2 with alternating current, the frequency in the output 'of coils I5 will be double that of the exciting voltage. The exciting voltage being at 400 cycles, the output of coils I5 will be at 800 cycles.

It has been stated above that in each halfcycle of excitation of winding II, there is an interval during which the inner portions of legs I2 is saturated and an interval during which these portions are unsaturated. When saturated, the earths flux cannot flow from one of legs I 2 to either or both of the other legs without going through air. The earths flux is driven out of legs I2; at least in the region-of coils in winding II by the presence of the flux due to the saturation current of winding I I, causing the number of lines of the earths flux cutting coils I5 to decrease, setting up a voltage pulse in coils I6. During one half-cycle of alternating current from source I3, current will rise sinusoidally from zero at zero degrees until saturation is attained and then to a maximum at 90 degrees, then fall to zero again at 180 degrees.

' If winding II is so chosen that the ampereturns are proper for saturating the proximate portion of legs I2 at 45 degrees, then from zero degrees to 45 degrees, the earths flux flows through legs I 2 in sequence without difllculty,

but the saturation characteristics of Permalloy and Mumetal" are such that a verysmall increase in current just at the threshold of saturation will cause saturation to take place. Thus, during the interval 45 degrees saturation due to current from alternator I3 causes the earths flux to leave legs I2 and flow through air until at 135 degrees the value of the current in winding II falls below the saturating value and the earths field re-enters legs I2, which now, due to their superior permeability and absence of saturating flux, aflord the earths flux a path of reluctance lower than the path in air. From 135 degrees until 225 degrees (second half-cycle), the earths flux will thread legs I2, and upon saturation at 225'degrees, it will be again forced to flow through air. In each half-cycle, at the 45, 135 and 225, 315 degree points, the earths flux is abruptly changed causing a pulse of voltv of its low moment of inertia, rotor 40 will be.

two pulses (of opposite sign) for every half cycle of excitation, the frequency of the current in coils I5 is double the excitation frequency. Resonance is obtaineddue to the inductive action oi the iron in the Autosyn stator II.

In Fig. 2, the two-phase induction motor of the present invention is shown in section and comprises a two-part housing 62 having an annular spacing ring such as a metal channel member 63 against which the housing members 62 are tightly drawn by means of upstanding screw threaded lugs 64, and screw member 65 which pass through holes in lugs 66. Annular ring 63 confines the laminated iron stator 34 through which are threaded the two-phase winding 61, in any conventional manner. The inner stator member 31 includes a stack of disc-like iron laminations,

0 carried by central core member 68 which has its outer end 68 upset by spinning or any other suitable method, so as to confine the laminations into a tightly packed stator member. Core member 68 has a central bore 1! which is counterbored at one end to receive a conventional ballbearing II. Cup-shaped rotor member 40 is disposed in the air gap space 38 with suilicient clearance between its cylindrical wall 39 and stator members 34 and 31 as to be freely rotatable in the air gap space 38. Shaft 4I is fixed to rotor member 40 by any'suitable means, such as the screw threaded nut and bolt arrangement, which is shown at I2. One portion of housing 62 contains a bearing member I3 in end-wall I4, and bearings II and I! support shaft 4|, so that it may be freely rotated within bore III of core member 68. A rotating electrical field is set up within stator 34 by means of two-phase current connected to the windings 15, for example, as shown schematically in Fig. l.

A ring I6 of insulating material such as Bakelite is mounted on the end face of one of housing parts 60, by means of a plurality of studs 11, and suitable terminals I8 are mounted thereon for connection of two-phase windings I! with an external circuit, such as that shown in Fig. 1. Although the connections of winding IE to terminals 18 are not shown, it will be understood that leads may be brought out through one 01 more apertures I9 of housing 60.

Rotor member 40 may be formed of any good conductive material, such as copper or aluminum, and as theiotating electrical field sets up a concentrated flux in stator 34 and traverses the air gap 38 to thread through stator memer ll,

' eddy currents will be set up in rotor 40 and the interaction of the magnetic field with the eddy currents of the rotating magnetic field will cause rotor 40 to be rotated in one direction or the other, at synchronous speed minus slip, depending upon the phase relation between the twophase windings. Rotor 40 includes no magnetic material and may be of thin gauged metal, so that its moment of inertia as compared with the moment of inertia of the usual iron rotor of an induction motor, will be extremely low. for example, on the order or /30 or less. By virtue started, stopped and reversed, with the minimum hunting or rotation of shaft 4|. This item is of extreme value in a compass system as herein described or in other navigational and control systems where the ability of an indicator, such as pointer 88, to come to rest at its proper course indication, without oscillation or hunting, is of importance.

The brushless coupling above described with reference to Fig. 1, is shown in detailed section in Fig. 3. The two parts of housing 88 are separated by spacing member 8|, which retains the stator portion I1, comprising iron laminations, and the usual Autosyn" windings of the Autosyn I8. Housing members 88 are retained in assembled relation by means of a plurality of stud screw members 82, which pass'through upstanding lug members 88 and fasten into screwthreaded portions 84. Shaft 2| passes transversely through housing portions 88, and is car ried by conventional ball bearings indicated generally at 85. Rotor member I! of iron laminations, carrying coil 28, is fixed by any conventional means, such as shoulder 81 and screwthreaded nut 88, so as to be rotatable with shaft 2|. Spaced from rotor I9 along shaft 2| is core member 22 of soft iron or other magnetic material, which is held by means of shoulder portion 88, and screw-threaded nut 88 and thus rotates with shaft 2|. Core member 22 carries primary winchng 23, the ends of which are connected to the ends of coil 28 by means of a pair of conductors 8|. Shell member 28 is held fixed within one of the housing portions 88, as shown by means of a plurality of screw stud members 82, which are tapped into the periphery of shell member 24. Secondary winding 25 is wound within shell member 28, and the ends thereof are brought out in any suitable manner for connection with an external circuit.

The flanged portions of core member 22 and shell member 24 are separated by an air gap 28 of small width, so that the magnetic material of members 22 and 24 will form a closed magnetic circuit encompassing primary winding 28 and secondary winding 28, with the lowest possible reluctance in the magnetic path. As core member 22 is of uniform configuration throughout, and as shell member 25 is likewise uniformly.

shaped throughout, and since windings 28 and 28 are wound uniformly within members 22 and 28, respectively, there will be faithful transfer of electrical energy from winding 23 to winding 28 regardless of angular disposition of shaft 2i, thus, as voltages induced in coil 28 of rotor I8 may vary with the angular displacement of rotor IS, with respect to stator II, the inductive coupling shown will permit a frictionless and, yet an efficient transfer of electrical energy from rotating shaft 2| to fixed shell member 28.

The indicator which includes scale 89 and pointer 48 may be considered as the master indicator. Remote indicators may be provided at any desired number of repeating stations for duplicating the indications of pointer- 88. A transmitting Autosyn," or other type of selfsynchronous transmitting motor (sometimes called an Autosyn" generator), such as 88, has a stator portion 88, shown schematically in Fig. l, and a rotor portion 85, likewise shown. Rotor 85 is fixed to shaft 2I and carries a coil member III 88, which is energized by alternator I8 through leads 81, 88 and I4. An Autosyn" receiving motor is contained in remote indicator 88, and leads I88 are connected to the rotor thereof, not shown, by the brush and slip ring connections I8I. The'stator portion of the Autosyn" receiver (not shown) in remote indicator 88 is connected in parallel to the stator portion of "Autosyn" 88 through leads I 82 and slip ring and brush connections I83. As indicated by the extensions of leads I88 and I82, other remote indicators may be connected in parallel to remote indicator 88. Housing I88 is fixed to a carrying vehicle in any conventional manner, and carries a pair of lubber lines I85, similar tolubber lines 88.

When the pilot at the master station heads the vehicle upon a given course, pointer I88 will indicate the course upon scale I81, and means are provided for permitting pointer I88 to be oriented after the fashion of pointer 88. Orientation of pointer I88 is obtained, merely by the turning of knob I88, which actuates the intermeshed pinions and gear arrangement I88, which coact with teeth or a ring gear II8 carried by housing of Autosyn 88. As dial or scale I8! is fixed with respect to this housing, rotation of knob I88 will cause scale I81 and pointer I88 to be turned together through any desired arc, and pointer I88 can be made to lie in parallel with lubber lines I88 to indicate an on" course condition of the course, and then any deviation of pointer I88 to the right or left of this parallel condition will indicate a deviation of the craft from the selected heading.

While only one embodiment of the navigating system of the present invention has been shown and described, it is to be understood that the invention is not limited thereto, but only by the scope of the appended claim.

' What is claimed is:

In a compass comprising a member sensitive to the directive force of the earth's magnetic field, a two-phase induction motor controlled by said member, an indicating device operated by said motor, means to refer indications of said indicating device to a selected axis of a carrying craft, a portion of said-indicating device being carried by a shaft driven by said motor, a second motor having a stator portion electrically connected to portionsof said member, and a rotor in which are induced voltages representative of the direction of the earth's magnetic field, connections between said rotor and one phase of said induction motor, an alternating current source for energizing the second phase of said motor, said phases being wound upon an exterior stator portion of said motor, said motor also having an interior portion and a rotor member connected to said shaft, said rotor member being of conductive material and having an annular portion thereof disposed between said exterior and interior stators so that upon energization of 

